fix: resolve all nlreturn linter errors

Add blank lines before return statements in all files to satisfy
the nlreturn linter. This improves code readability by providing
visual separation before return statements.

Changes made across 24 files:
- internal/cli/*.go
- internal/secret/*.go
- internal/vault/*.go
- pkg/agehd/agehd.go
- pkg/bip85/bip85.go

All 143 nlreturn issues have been resolved.

pkg/agehd/agehd.go

@@ -21,11 +21,11 @@ import (
 )
 
 const (
-	purpose      = uint32(83696968)  // fixed by BIP-85 ("bip")
-	vendorID     = uint32(592366788) // berlin.sneak
-	appID        = uint32(733482323) // secret
-	hrp          = "age-secret-key-" // Bech32 HRP used by age
-	x25519KeySize = 32               // 256-bit key size for X25519
+	purpose       = uint32(83696968)  // fixed by BIP-85 ("bip")
+	vendorID      = uint32(592366788) // berlin.sneak
+	appID         = uint32(733482323) // secret
+	hrp           = "age-secret-key-" // Bech32 HRP used by age
+	x25519KeySize = 32                // 256-bit key size for X25519
 )
 
 // clamp applies RFC-7748 clamping to a 32-byte scalar.